SF: Short-circuit scheduler content detection

Avoid registering, recording, partitioning, and transforming layers
for content detection in the scheduler if there is a single refresh
rate config.

Dump content detection version, and layer history stats.

Bug: 158780872
Test: No layer history on crosshatch, ARC, etc.
Test: dumpsys SurfaceFlinger --vsync
Test: libsurfaceflinger_unittest
Change-Id: Ia23a35cd6aa0cb117b19c98f5d0af8c14836430e
diff --git a/services/surfaceflinger/Scheduler/LayerHistory.h b/services/surfaceflinger/Scheduler/LayerHistory.h
index 228b8a0..128699b 100644
--- a/services/surfaceflinger/Scheduler/LayerHistory.h
+++ b/services/surfaceflinger/Scheduler/LayerHistory.h
@@ -22,6 +22,7 @@
 
 #include <memory>
 #include <mutex>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -71,6 +72,7 @@
     virtual Summary summarize(nsecs_t now) = 0;
 
     virtual void clear() = 0;
+    virtual std::string dump() const = 0;
 };
 
 namespace impl {
@@ -97,6 +99,7 @@
     android::scheduler::LayerHistory::Summary summarize(nsecs_t now) override;
 
     void clear() override;
+    std::string dump() const override;
 
 private:
     friend class android::scheduler::LayerHistoryTest;
@@ -155,6 +158,7 @@
     android::scheduler::LayerHistory::Summary summarize(nsecs_t /*now*/) override;
 
     void clear() override;
+    std::string dump() const override;
 
 private:
     friend android::scheduler::LayerHistoryTestV2;